Window protector for sputter etching of metal layers

ABSTRACT

An inductively coupled plasma processing apparatus includes a chamber having a top opening. A window seals the top opening of the chamber, and the window has an inner surface that is exposed to an internal region of the chamber. A window protector for protecting the inner surface of the window is disposed within the chamber. The window protector is configured to prevent conductive etch byproducts from being deposited on the inner surface of the window in the form of a continuous loop. In one alternative embodiment, a plurality of window protectors is affixed to the inner surface of the window. In another embodiment, the window has a plurality of T-shaped or dovetail slots formed therein. In yet another embodiment, a plurality of rectangular slots is formed in the window and a window protector having corresponding slots is mounted against the inner surface of the window.

BACKGROUND OF THE INVENTION

The present invention relates generally to semiconductor fabrication and, more particularly, to a window protector for sputter etching of metal layers.

In inductively coupled plasma etching tools (e.g., the 2300 Versys® etch system commercially available from Lam Research Corporation of Fremont, Calif.), electrically conducting films are deposited on the dielectric window during some etch processes. An example of such an etch process is the sputter etching of platinum electrodes in a magnetoresistive random access memory (MRAM) stack. The dielectric window is typically made of an insulating dielectric material such as fused silica or alumina. The deposition of an electrically conducting film on the dielectric window reduces the inductive coupling between the RF coil and the plasma, causing a reduction in the plasma density and eventually making it impossible to sustain the plasma. When the conducting film begins to interfere with the etch process, the etch chamber must be opened and the dielectric window must be cleaned.

U.S. patent No. U.S. Pat. No. 6,280,563 B1 to Baldwin, Jr. et al. discloses a plasma device in which a non-magnetic metal plate is formed on the lower surface of the dielectric window, i.e., the surface of the dielectric window disposed inside the chamber (see, e.g., reference numeral 56 in FIG. 1). The non-magnetic metal plate has a configuration that includes a plurality of radially extending slots. These slots disrupt eddy currents that would otherwise flow in the metal plate. The metal plate would block the deposition of a conducting film on the portion of the dielectric window covered by the metal plate, but this may not prevent inductive coupling between the RF coil and the plasma from being blocked during an etch process. For instance, if the deposited conducting film conformally coats the surface of the metal plate and the surface of the dielectric window that is exposed by the radial slots in the metal plate, then a continuous loop of conducting film would be formed and this continuous loop of conducting film may be sufficient to block the inductive coupling between the RF coil and the plasma. Alternatively, if the deposited conducting film fills in the radial slots in the metal plate, then a continuous conducting structure including the metal plate and the deposited conductive film would be formed and this continuous conducting structure may be sufficient to block the inductive coupling between the RF coil and the plasma.

In view of the foregoing, there is a need to protect a dielectric window from having a continuous loop of conducting film deposited thereon during an etch process.

SUMMARY OF THE INVENTION

Broadly speaking, the present invention fills this need by providing an inductively coupled plasma processing apparatus that is configured to prevent conductive etch byproducts from being deposited on the inner surface of the window in the form of a continuous loop. As explained in more detail later, the plasma processing apparatus may include a window protector disposed within the chamber or a plurality of window protectors disposed within the chamber. Alternatively, the window may have a plurality of T-shaped or dovetail slots formed therein. The window also may have a plurality of rectangular slots formed therein, with a window protector having corresponding slots being mounted against the inner surface of the window.

In accordance with one aspect of the present invention, a first inductively coupled plasma processing apparatus is provided. This plasma processing apparatus includes a chamber having a top opening. A window seals the top opening of the chamber, and the window has an inner surface that is exposed to an internal region of the chamber. A window protector for protecting the inner surface of the window is disposed within the chamber. The window protector is configured to prevent conductive etch byproducts from being deposited on the inner surface of the window in the form of a continuous loop.

In one embodiment, the window protector is disposed within the chamber such that the window protector is separated from the inner surface of the window by a distance in a range from 0.02 inch to 0.1 inch. In one embodiment, the window protector is comprised of a conducting material. In one embodiment, the window protector is comprised of an insulating material. In one embodiment, the window protector is comprised of a material having good adhesion properties. In one embodiment, the window protector is in the shape of a Faraday shield.

In accordance with another aspect of the present invention, a second inductively coupled plasma processing apparatus is provided. This plasma processing apparatus includes a chamber having a top opening. A chuck for holding a wafer being processed is disposed within the chamber. A window seals the top opening of the chamber, and the window has an inner surface that is exposed to an internal region of the chamber. A plurality of window protectors is affixed to the inner surface of the window. Each of the plurality of window protectors has an upper surface that is affixed to the inner surface of the window and a lower surface that is exposed to the internal region of the chamber. The lower surface of each window protector has a cross-sectional width that is larger than a cross-sectional width of the upper surface of each window protector. In addition, the plurality of window protectors is arranged on the inner surface of the window in a spaced apart relationship such that each region of the inner surface of the window that is in a line of sight of the wafer being processed is separated from an adjacent window protector by a region of the inner surface of the window that is not in the line of sight of the wafer being processed.

In one embodiment, each of the plurality of window protectors is comprised of a nonmagnetic metal. In one embodiment, a cross section of each of the plurality of window protectors is T-shaped.

In accordance with yet another aspect of the present invention, a third inductively coupled plasma processing apparatus is provided. This plasma processing apparatus includes a chamber having a top opening. A window seals the top opening of the chamber, and the window has an inner surface that is exposed to an internal region of the chamber. The inner surface of the window has a plurality of slots formed therein, with the plurality of slots being arranged in the shape of a Faraday shield. Each of the plurality of slots has a slot opening and a slot width, with the slot width being larger than the slot opening.

In one embodiment, each of the plurality of slots is a T-shaped slot or a dovetail slot cut directly into the window. In one embodiment, each of the plurality of slots is a rectangular slot cut directly into the window, and the plasma processing apparatus further includes a window protector mounted against the inner surface of the window. The window protector has a plurality of slots formed therein, with the plurality of slots formed in the window protector corresponding to the plurality of slots formed in the window. Each of the plurality of slots formed in the window has a first slot width and each of the plurality of slots formed in the window protector has a second slot width, with the first slot width being larger than the second slot width.

It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the principles of the invention.

FIG. 1A is a simplified schematic cross-section showing a plasma processing apparatus in accordance with one embodiment of the invention.

FIG. 1B is a simplified schematic cross-section showing a plasma processing apparatus in accordance with another embodiment of the invention.

FIG. 2 is a top view of the window protector shown in FIG. 1A that shows additional details of the window protector.

FIG. 3A is a simplified cross-sectional view of a plasma processing apparatus that illustrates how the window protector shown in FIG. 1A shields the dielectric window as material is sputtered from a wafer during a plasma processing operation.

FIG. 3B shows the shape of the sputtered material deposited on the inner surface of the dielectric window in accordance with one embodiment of the invention.

FIG. 4 is a simplified cross-sectional view of a plasma processing apparatus that illustrates how the window protector shown in FIG. 1B shields the dielectric window as material is sputtered from a wafer during a plasma processing operation.

FIG. 5A illustrates an alternative embodiment of the invention in which T-shaped or dovetail slots are cut directly into the dielectric window.

FIG. 5B illustrates an alternative embodiment of the invention in which rectangular slots are cut directly into the dielectric window and a window protector having corresponding slots is mounted against the inner surface of the dielectric window.

FIG. 6 illustrates an embodiment of the invention in which a single window protector is mounted directly against the inner surface of the dielectric window.

FIG. 7 illustrates an embodiment of the invention in which a plurality of window protectors is disposed just below the inner surface of the dielectric window.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Several exemplary embodiments of the invention will now be described in detail with reference to the accompanying drawings.

FIG. 1A is a simplified schematic cross-section showing an inductively coupled plasma processing apparatus in accordance with one embodiment of the invention. As shown in FIG. 1A, semiconductor wafer 10 is mounted on chuck 12 disposed in chamber 100, which is defined by walls of a housing. Coil 14 is supported above dielectric window 16 by, e.g., spacers (not shown), which may be formed of a suitable insulating material. Dielectric window 16 is typically formed of an insulating dielectric material such as fused silica or alumina (Al₂O₃). The primary role of dielectric window 16 is to seal the top opening of chamber 100 so that a vacuum can be maintained within the chamber during processing. In operation, a reactant gas is fed into chamber 100 though a suitable gas inlet (not shown). High frequency power from RF power supply 18 is applied to coil 14. The high frequency (RF) current passing through coil 14 induces an electromagnetic field in chamber 100, and the electromagnetic field acts on the reactant gas to generate a plasma. Additional details regarding the structure and operation of an inductively coupled plasma processing apparatus are set forth in U.S. patent No. U.S. Pat. No. 6,280,253 B1, the disclosure of which is incorporated herein by reference.

Window protector 20, which shields a portion of dielectric window 16 from etch byproducts, i.e., material sputtered from the wafer, is disposed within chamber 100 just below inner surface 16 a of dielectric window 16. As will be explained in more detail later, window protector 20 is configured to prevent conductive etch byproducts from being deposited on inner surface 16 a of dielectric window 16 in the form of a continuous loop. The gap between window protector 20 and inner surface 16 a of dielectric window should be narrow enough to avoid any significant plasma generation within the gap, but wide enough to prevent the conductive films deposited on the window protector and the dielectric window from merging with other conductive materials. In one embodiment, the gap between window protector 20 and inner surface 16 a of dielectric window 16 is between a few hundredths of an inch (e.g., 0.02-0.03 inch) and a tenth of an inch (0.1 inch).

The material from which window protector 20 is made may be selected based on a number of factors including compatibility with the plasma and adhesion properties relative to the etch byproduct, i.e., the material being sputtered from the wafer. The adhesion of material sputtered from the wafer on the window protector is a consideration because material flaking off the window protector will limit the mean time between cleans (MTBC) for the plasma processing apparatus. By way of example, the window protector may be made of an insulating material, a conducting material, or a material having good adhesion properties. As used herein, the phrase “a material having good adhesion properties” refers to a material to which the sputtered film has high adhesion.

Exemplary insulating materials include the same materials from which the dielectric window is typically made, e.g., fused silica, aluminum oxide (Al₂O₃), aluminum nitride (AlN), and high-resistivity silicon carbide (SiC). Exemplary conducting materials include the same materials from which the housing defining the chamber is typically made, e.g., aluminum and anodized aluminum. Regarding materials having good adhesion properties, as a general rule, thin films of material adhere better to other materials that have the same (or about the same) coefficient of thermal expansion, so that stress does not build up when the materials are heated or cooled. One example of a material having good adhesion properties is, of course, the same material. Thus, in the case of a sputtered platinum film, the sputtered platinum film might adhere well to a platinum (or platinum-coated) window protector.

Window protector 20 is supported within chamber 100 by support members 22. As shown in FIG. 1A, support members 22 are fastened to the sidewall of the housing defining chamber 100. It will be apparent to those skilled in the art that the support members need not be fastened to the sidewall of the housing and that any suitable mechanical support scheme may be used to support window protector 20 within chamber 100. Additional details regarding the structure and functionality of the window protector are described later with reference to FIGS. 2, 3A, and 3B.

FIG. 1B is a simplified schematic cross-section showing an inductively coupled plasma processing apparatus in accordance with another embodiment of the invention. The plasma processing apparatus shown in FIG. 1B is the same as that shown in FIG. 1A, except that a plurality of window protectors 20′ have been substituted for window protector 20. As shown in FIG. 1B, a plurality of window protectors 20′ are affixed to dielectric window 16. In particular, the upper surface 20′-1 of each window protector 20′ is affixed to inner surface 16 a of dielectric window 16. Window protectors 20′ may be affixed to inner surface 16 a of dielectric window 16 using any suitable fastening technique. Window protectors 20′ may be arranged on the inner surface 16 a of dielectric window 16 in any pattern that is effective to prevent conductive etch byproducts from being deposited on the inner surface of the dielectric window in the form of a continuous loop. In one embodiment, each of window protectors 20′ has a cross section that is T-shaped. With a T-shaped configuration, the lower surface 20′-2 of each window protector 20′, i.e., the surface that is exposed to the internal region of chamber 100, has a cross-sectional width that is larger than the cross-sectional width of the upper surface 20′-1 of each window protector 20′. Additional details regarding the structure and functionality of the plurality of window protectors 20′ are described later with reference to FIG. 4.

FIG. 2 is a top view of window protector 20 shown in FIG. 1A that shows additional details of the window protector. As shown in FIG. 2, window protector 20 is a relatively thin sheet of material in the physical shape of a Faraday shield. More particularly, window protector 20 has a circular shape and is provided with a number of radially extending slots 20 a. The radially extending slots 20 a prevent large-scale electrical currents from flowing in a circular pattern, i.e., a continuous loop, in window protector 20 (when the window protector is formed of a conducting material), and thereby render the window protector relatively “transparent” to the inductive coupling between coil 14 and the plasma. In one embodiment, the thickness of the window protector is one-eighth of an inch. In one embodiment, the diameter of window protector 20 is either the same as or slightly larger than the diameter of the wafer being processed. Those skilled in the art will appreciate that the size of the window protector may be varied to suit the needs of particular applications.

As used herein, the phrases “a continuous loop” and a “continuous loop of material” refer to a circular band of material that is capable of allowing induced electric currents sufficient to impede the inductive coupling between the coil and the plasma to flow in a circular pattern. Those skilled in the art will recognize that induced electric currents in very small loops likely will not be sufficient to impede the inductive coupling between the coil and the plasma. By way of example, a small loop at the center of window protector 20 (see FIG. 2) will not impede the inductive coupling between the coil and the plasma because the azimuthal, i.e., circular, induced electric field of an inductively coupled plasma is zero on the central axis. In contrast, if an induced electric current were to flow in a larger loop, i.e., a loop large enough that the loop had to cross one or more of the radially extending slots 20 a in window protector 20 (see FIG. 2), then this induced electric current would be sufficient to impede the inductive coupling between the coil and the plasma.

FIG. 3A is a simplified cross-sectional view of a plasma processing apparatus that illustrates how window protector 20 shown in FIG. 1A shields dielectric window 16 as material is sputtered from a wafer during a inductively coupled plasma processing operation. The upwardly directed arrows shown in FIG. 3A depict exemplary lines of sight from wafer 10 to window protector 20 and dielectric window 16. When material is sputtered from wafer 10 during a plasma processing operation, the sputtered material will likely be deposited on any structure within the line of sight of the wafer. As shown in FIG. 3A, sputtered material 22 a is deposited on the exposed inner surface of window protector 20 that is in the line of sight of wafer 10. The shape of sputtered material 22 a corresponds to the shape of window protector 20 (see FIG. 2). As such, sputtered material 22 a has gaps defined therein and therefore does not form a continuous loop of material. Sputtered material 22 b is deposited on inner surface 16 a of dielectric window 16 because portions of the inner surface of the dielectric window are in the line of sight of wafer 10 due to the presence of radially extending slots 20 a in window protector 20. As shown in FIG. 3A, no material is sputtered on the portion of inner surface 16 a that is not in the line of sight of the wafer due to the presence of window protector 20. The shape of sputtered material 22 b deposited on inner surface 16 a of dielectric window 16 is shown in FIG. 3B and corresponds to the shapes of slots 20 a formed in window protector 20. As such, sputtered material 22 b also has gaps and therefore does not form a continuous loop of material.

As noted above, neither sputtered material 22 a nor sputtered material 22 b is in the form of a continuous loop. In addition, sputtered material 22 a is electrically insulated from sputtered material 22 b by the gap between window protector 20 and inner surface 16 a of dielectric window 16. Consequently, sputtered material 22 a and sputtered material 22 b should not block the inductive coupling between the coil and the plasma. Thus, a significant thickness of sputtered material 22 a and 22 b can accumulate without adversely affecting plasma generation, and the mean time between cleans (MTBC) for the plasma processing apparatus can be increased.

FIG. 4 is a simplified cross-sectional view of an inductively coupled plasma processing apparatus that illustrates how window protector 20′ shown in FIG. 1B shields dielectric window 16 as material is sputtered from a wafer during a plasma processing operation. The upwardly directed arrows shown in FIG. 4 depict exemplary lines of sight from wafer 10 to window protector 20′ and dielectric window 16. As discussed above with reference to FIG. 3A, when material is sputtered from wafer 10 during a plasma processing operation, the sputtered material will likely be deposited on any structure within the line of sight of the wafer. As shown in FIG. 4, sputtered material 22 a′ is deposited on the exposed inner surface 20′-2 of each window protector 20′. As window protectors 20′ are separated from one another, sputtered material 22 a′ includes a number of separated pieces and therefore is not in the form a continuous loop of material. Sputtered material 22 b′ is deposited on inner surface 16 a of dielectric window 16 because portions of the inner surface of the dielectric window are in the line of sight of wafer 10 due to the spaces between adjacent window protectors 20′. As shown in FIG. 4, no material is sputtered on portions 16 a-1 of the inner surface 16 a of dielectric window 16 because these portions of the inner surface of the dielectric window are not in the line of sight of wafer 10 due to the T-shaped configuration of window protectors 20′. Thus, sputtered material 22 b′ includes a number of separated pieces, with each piece of sputtered material 22 b′ being insulated from the adjacent window protectors 20′ by a portion 16 a-1 on which no material is sputtered.

As both sputtered material 22 a′ and sputtered material 22 b′ include a number of separated pieces, neither of these sputtered materials is in the form of a continuous loop. In addition, sputtered material 22 a′ is electrically insulated from sputtered material 22 b′ and window protectors 20′ (which may be formed of a conducting material, e.g., a nonmagnetic metal) by the portions 16 a-1 of the inner surface 16 a of dielectric window 16 on which no material is sputtered. Consequently, sputtered material 22 a′ and sputtered material 22 b′ should not block the inductive coupling between the coil and the plasma. Thus, a significant thickness of sputtered material 22 a′ and 22 b′ can accumulate without adversely affecting plasma generation, and the mean time between cleans (MTBC) for the plasma processing apparatus can be increased.

It will be apparent to those skilled in the art that the invention may be implemented in ways other than those illustrated in FIGS. 1A-4. By way of example, two alternative ways of implementing the invention are shown in FIGS. 5A and 5B. Referring first to FIG. 5A, dielectric window 16′ has a T-shaped slot 16′-1 cut directly into the window. In one embodiment, dielectric window 16′ includes a plurality of slots 16′-1, with the slots being arranged in the shape of a Faraday shield. Those skilled in the art will recognize that the shape of slot 16′-1 is not limited to the T-shape shown in FIG. 5A and that other shapes having a slot opening that is narrower than the slot width also may be used, e.g., a dovetail shape (see FIG. 6). During a plasma etching operation using dielectric window 16′, conductive etch byproducts will be deposited on the inner surfaces 16 a′ of the window as well as on the portions of the surfaces of slot 16′-1 that are in the line of sight of the wafer (the wafer is not shown in FIG. 5A). No conductive etch byproducts will be deposited on the portions of the surfaces of slots 16′-1 that are not in the line of sight of the wafer, i.e., the portions of the surfaces that are blocked from the wafer by the narrow openings of the slots. The portions of the surfaces of the slots on which no conductive etch byproducts are deposited prevent the conductive etch byproducts deposited on the inner surface of the dielectric window from making electrical contact with the conductive etch byproducts deposited on the surfaces of the slots. In this manner, the slots in the dielectric window prevent the conductive etch byproducts from being deposited on the inner surface of the window in the form of a continuous loop. Consequently, the conductive etch byproducts deposited on the dielectric window should not block the inductive coupling between the coil and the plasma.

Turning to FIG. 5B, dielectric window 16″ has a rectangular slot 16″-1 cut directly into the window. In one embodiment, dielectric window 16″ includes a plurality of slots 16″-1, with the slots being arranged in the shape of a Faraday shield. Window protector 20″ is mounted directly against inner surface 16″a of dielectric window 16″. In one embodiment, window protector 20″ is provided with a number of radially extending slots 20″a that correspond to slots 16″-1 in dielectric window 16″, except that the width of slots 20″a is smaller than the width of slots 16″-1. During a plasma etching operation using dielectric window 16″ and window protector 20″, conductive etch byproducts will be deposited on the exposed inner surface of the window protector as well as on the portions of the surfaces of slots 16″-1 that are in the line of sight of the wafer (the wafer is not shown in FIG. 5B). No conductive etch byproducts will be deposited on the portions of the surfaces of slots 16″-1 that are not in the line of sight of the wafer, i.e., the portions of the surfaces that are blocked from the wafer by the narrow openings of the slots in the window protector. The portions of the surfaces of the slots in the dielectric window on which no conductive etch byproducts are deposited prevent the conductive etch byproducts deposited on the inner surface of the window protector from making electrical contact with the conductive etch byproducts deposited on the surfaces of the slots in the window. In this manner, the slots in the dielectric window, in combination with the slots in the window protector, prevent the conductive etch byproducts from being deposited on the inner surface of the window protector and slots in the window in the form of a continuous loop. Consequently, the conductive etch byproducts deposited on the window protector and the dielectric window should not block the inductive coupling between the coil and the plasma.

FIG. 6 illustrates an embodiment of the invention in which a single window protector is mounted directly against the inner surface of the dielectric window. As shown in FIG. 6, window protector 20″-1 is mounted against dielectric window 16 using a suitable mechanical support scheme. Window protector 20″-1 may have the same configuration as window protector 20 shown in FIGS. 1A and 2, but is provided with a number of radially extending slots 20″-1 a, which have a dovetail-shaped cross section. During a plasma etching operation, conductive etch byproducts will be deposited on the exposed surfaces of window protector 20″-1 a and the portions of inner surface 16 a of dielectric window 16 that are in the line of sight of the wafer. Neither of these deposits will be in the form of a continuous loop due to the configuration of window protector 20″-1. No conductive etch byproducts will be deposited on the portions of the inner surface 16 a of dielectric window 16 that are not in the line of sight of the wafer, i.e., the portions of the inner surface of the dielectric window that are blocked from the wafer by the narrow openings of the slots. The portions of the inner surface 16 a of the dielectric window 16 on which no conductive etch byproducts are deposited prevent the conductive etch byproducts deposited on the inner surface of the dielectric window from making electrical contact with the conductive etch byproducts deposited on the exposed surfaces of window protector 20″-1. In this manner, the shaped cross section of slots 20″-1 a in window protector 20″-1 prevent the conductive etch byproducts from being deposited on the window protector and the inner surface of the dielectric window in the form of a continuous loop. Consequently, neither the conductive etch byproducts deposited on the window protector nor the conductive etch byproducts deposited on the dielectric window should block the inductive coupling between the coil and the plasma. It will be apparent to those skilled in the art that radially extending slots 20″-1 a may have shaped cross sections other than the dovetail shape shown in FIG. 6. By way of example, slots 20″-1 a also may have a T-shaped cross section.

FIG. 7 illustrates an embodiment of the invention in which a plurality of window protectors is disposed just below the inner surface of the dielectric window. As shown in FIG. 7, a plurality of window protectors 20′-x is supported within the chamber such that there is a gap between each window protector and the inner surface 16 a of dielectric window 16. In one embodiment, the gap between window protectors 20′-x and inner surface 16 a of dielectric window 16 is between a few hundredths of an inch (e.g., 0.02-0.03 inch) and a tenth of an inch (0.1 inch). Each of the window protectors 20′-x has a rectangular cross section and may be supported within the chamber using any suitable support scheme. During a plasma etching operation, sputtered material 22 a″ is deposited on the exposed inner surface 20′-x1 of each window protector 20′-x. As window protectors 20′-x are separated from one another, sputtered material 22 a″ includes a number of separated pieces and therefore is not in the form a continuous loop of material. Sputtered material 22 b″ is deposited on inner surface 16 a of dielectric window 16 because portions of the inner surface of the dielectric window are in the line of sight of the wafer (not shown in FIG. 7) due to the spaces between adjacent window protectors 20′-x. As shown in FIG. 7, no material is sputtered on portions 16 a-1 of the inner surface 16 a of dielectric window 16 because these portions of the inner surface of the dielectric window are not in the line of sight of the wafer due to the combination of the rectangular configuration of window protectors 20′-x and the gap between each window protector and the inner surface of the dielectric window. Thus, sputtered material 22 b″ includes a number of separated pieces.

As both sputtered material 22 a″ and sputtered material 22 b″ include a number of separated pieces, neither of these sputtered materials is in the form of a continuous loop. In addition, sputtered material 22 b″ is electrically insulated from sputtered material 22 a″ and window protectors 20′-x (which may be formed of a conducting material) by the gap between the window protectors and the inner surface of the dielectric window. Consequently, sputtered material 22 a″ and sputtered material 22 b″ should not block the inductive coupling between the coil and the plasma. Thus, a significant thickness of sputtered material 22 a″ and 22 b″ can accumulate without adversely affecting plasma generation, and the mean time before cleaning (MTBC) for the plasma processing apparatus can be increased.

As used in connection with the description of the invention, the phrase “means for protecting the inner surface of the window from having conductive etch byproducts deposited thereon in the form of a continuous loop” includes all of the window protection structures shown and described herein. These structures include a single window protector separated from the window by a gap (as shown in FIGS. 1A and 3A), a single window protector having a shaped cross section in contact with the window (as shown in FIG. 6), a plurality of window protectors separated from the window (as shown in FIG. 7), a plurality of window protectors having a shaped cross section in contact with the window (as shown in FIGS. 1B and 4), and a window having slots cut directly therein (as shown in FIGS. 5A (without a window protector) and 5B (with a window protector)).

In summary, the present invention provides an inductively coupled plasma processing apparatus that prevents conductive etch byproducts from being deposited on the inner surface of the window in the form of a continuous loop. The invention has been described herein in terms of several exemplary embodiments. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention. The embodiments and preferred features described above should be considered exemplary, with the invention being defined by the appended claims and equivalents thereof. 

1. An inductively coupled plasma processing apparatus, comprising: a chamber having a top opening; a window that seals the top opening of the chamber, the window having an inner surface that is exposed to an internal region of the chamber; and a window protector for protecting the inner surface of the window disposed within the chamber, the window protector being configured to prevent conductive etch byproducts from being deposited on the inner surface of the window in the form of a continuous loop.
 2. The plasma processing apparatus of claim 1, wherein the window protector is disposed within the chamber such that the window protector is separated from the inner surface of the window by a distance in a range from 0.02 inch to 0.1 inch.
 3. The plasma processing apparatus of claim 1, wherein the window protector is comprised of a conducting material.
 4. The plasma processing apparatus of claim 1, wherein the window protector is comprised of an insulating material.
 5. The plasma processing apparatus of claim 1, wherein the window protector is comprised of a material having good adhesion properties.
 6. An inductively coupled plasma processing apparatus, comprising: a chamber having a top opening; a window that seals the top opening of the chamber, the window having an inner surface that is exposed to an internal region of the chamber; and a window protector for protecting the inner surface of the window disposed within the chamber, the window protector being in the shape of a Faraday shield, and the window protector being separated from the inner surface of the window by a distance in a range from 0.02 inch to 0.1 inch.
 7. An inductively coupled plasma processing apparatus, comprising: a chamber having a top opening; a chuck for holding a wafer being processed disposed within the chamber; a window that seals the top opening of the chamber, the window having an inner surface that is exposed to an internal region of the chamber; and a plurality of window protectors affixed to the inner surface of the window, each of the plurality of window protectors having an upper surface that is affixed to the inner surface of the window and a lower surface that is exposed to the internal region of the chamber, the lower surface of each window protector having a cross-sectional width that is larger than a cross-sectional width of the upper surface of each window protector, and the plurality of window protectors being arranged on the inner surface of the window in a spaced apart relationship such that each region of the inner surface of the window that is in a line of sight of the wafer being processed is separated from an adjacent window protector by a region of the inner surface of the window that is not in the line of sight of the wafer being processed.
 8. The plasma processing apparatus of claim 7, wherein each of the plurality of window protectors is comprised of a nonmagnetic metal.
 9. The plasma processing apparatus of claim 7, wherein a cross section of each of the plurality of window protectors is T-shaped.
 10. An inductively coupled plasma processing apparatus, comprising: a chamber having a top opening; and a window that seals the top opening of the chamber, the window having an inner surface that is exposed to an internal region of the chamber, the inner surface of the window having a plurality of slots formed therein, the plurality of slots being arranged in the shape of a Faraday shield, and each of the plurality of slots having a slot opening and a slot width, with the slot width being larger than the slot opening.
 11. The plasma processing apparatus of claim 10, wherein each of the plurality of slots is a T-shaped slot or a dovetail slot cut directly into the window.
 12. The plasma processing apparatus of claim 10, wherein each of the plurality of slots is a rectangular slot cut directly into the window, and the plasma processing apparatus further comprises a window protector mounted against the inner surface of the window, the window protector having a plurality of slots formed therein, the plurality of slots formed in the window protector corresponding to the plurality of slots formed in the window, each of the plurality of slots formed in the window having a first slot width and each of the plurality of slots formed in the window protector having a second slot width, the first slot width being larger than the second slot width.
 13. The plasma processing apparatus of claim 12, wherein the window protector is comprised of a conducting material.
 14. The plasma processing apparatus of claim 12, wherein the window protector is comprised of an insulating material.
 15. The plasma processing apparatus of claim 12, wherein the window protector is comprised of a material having good adhesion properties.
 16. An inductively coupled plasma processing apparatus, comprising: a chamber having a top opening; a window that seals the top opening of the chamber, the window having an inner surface that is exposed to an internal region of the chamber; and means for protecting the inner surface of the window from having conductive etch byproducts deposited thereon in the form of a continuous loop. 